Conventional optical sensors utilize spherical domes and flat windows in order to protect optical systems from environmental effects such as rain, humidity, etc. As used herein, the term "conformal" optics describe optical systems that are designed with the operational environment as the primary consideration and the optical imaging properties as a secondary concern. As a result, conformal domes and windows for missile and airborne fire control systems are driven by aerodynamic performance issues, e.g. decreased aerodynamic drag, increased missile velocity and extended operational range, and result in highly aspheric dome geometries that are more elongated in shape.
A major disadvantage of these highly aspheric surfaces is the large aberrations they produce in the transmitted optical wave front. In addition, the inherent asymmetry of conformal surfaces leads to variations in the aberration content presented to the optical sensor as it is gimballed across the field of regard. These two factors degrade the sensor's ability to properly image targets of interest and hence undermine the overall system performance. Consequently, the aerodynamic advantages of conformal domes and windows cannot be realized in practical systems unless dynamic aberration correction techniques are developed to restore adequate optical imaging capabilities.
Flexible mirrors have been used as defocus elements in optical missile seekers, e.g. to defocus the imagery for image normalization purposes. Deformable mirrors have been used as adaptive optical elements in astronomical telescopes. U.S. Pat. Ser. No. 4,773,748 describes dynamically controlled deformable mirrors for use in applications such as projection systems.